RESUMEN

We demonstrate two efficient processing techniques for Nyquist signals, namely computation of signals using dynamic precision as well as arbitrary rational oversampling factors. With these techniques along with massively parallel processing it becomes possible to generate and receive high data rate Nyquist signals with flexible symbol rates and bandwidths, a feature which is highly desirable for novel flexgrid networks. We achieved maximum bit rates of 252 Gbit/s in real-time.

RESUMEN

Nyquist sinc-pulse shaping provides spectral efficiencies close to the theoretical limit. In this paper we discuss the analogy to optical orthogonal frequency division multiplexing and compare both techniques with respect to spectral efficiency and peak to average power ratio. We then show that using appropriate algorithms, Nyquist pulse shaped modulation formats can be encoded on a single wavelength at speeds beyond 100 Gbit/s in real-time. Finally we discuss the proper reception of Nyquist pulses.

Asunto(s)

RESUMEN

Real-time OFDM transmitters breaking the 100 Gbit/s barrier require high-performance, usually FPGA-based digital signal processing. Especially the Fourier transform as a key operation of any OFDM system must be optimized with respect to performance and chip area utilization. Here, we demonstrate an alternative to the widely adopted fast Fourier transform algorithm. Based on an extensive yet optimized use of pre-set look-up tables, our FPGA implementation supports fast reconfigurable channel equalization and switching times in the nanosecond range without re-loading any code. We demonstrate the potential of the concept by realizing the first real-time single polarization OFDM transmitter generating a 101.5 Gbit/s data stream by modulating 58 subcarriers with 16QAM.

Asunto(s)

RESUMEN

A practical scheme to perform the fast Fourier transform in the optical domain is introduced. Optical real-time FFT signal processing is performed at speeds far beyond the limits of electronic digital processing, and with negligible energy consumption. To illustrate the power of the method we demonstrate an optical 400 Gbit/s OFDM receiver. It performs an optical real-time FFT on the consolidated OFDM data stream, thereby demultiplexing the signal into lower bit rate subcarrier tributaries, which can then be processed electronically.

RESUMEN

We demonstrate a regenerative optical grooming switch for buffer-less interconnection of metro/access and metro/core ring networks with switching functionality in time, space and wavelength domain. Key functionalities of the router are the traffic aggregation with time-slot interchanging (TSI) functionality, the WDM-to-ODTM multiplexing and the OTDM-to-WDM demultiplexing of high-speed channel into lower bit-rate tributaries as well as multi-wavelength all-optical 2R regeneration of several higher-speed signals. BER and Q-factor measurements of different switching scenarios show excellent performance with no error floor and Q-factors above 21 dB.

RESUMEN

Possible association between the degree of iron load and glucose metabolism has been postulated by both in vivo and in vitro studies. Because skeletal muscle plays a major role in whole body glucose utilization, we evaluated the effect of iron chelators deferoxamine (DFO) and bipyridyl (Bip) on glucose metabolism and transport in cultured L6 muscle cells. Bip (0.1 mM) or DFO (0.5 mM) added for 24 h to the culture medium increased glucose consumption, lactate production, and [14C]glucose incorporation into glycogen by approximately twofold. 2-Deoxy-glucose uptake by L6 myotubes increased time dependently, reaching a 5-fold and 2.5-fold increase after 12 h for Bip and DFO, respectively. Insulin induced a 2.5-fold increase in glucose uptake in untreated cells, which was additive to the chelator's effect. Iron chelator-induced glucose transport stimulation was inhibited by cycloheximide (2.5 micrograms/ml), indicating dependence on de novo protein synthesis. Increases in GLUT-1 protein and mRNA concentration, without changes in GLUT-4, were found to be responsible for iron chelator effects. We conclude that L6 cells adapt to reduction in iron availability by increasing glucose utilization through an enhanced expression of GLUT-1, without losing their physiological response to insulin.

Asunto(s)

RESUMEN

The effects of various doses of indomethacin and ketoprofen as compared with placebo were examined in 100 oligospermic patients who participated in this study. It was found that the treatment increased sperm count, sperm motility, and fertilizing capacity. The radioimmunoassay examination showed an increase in plasma follicle-stimulating hormone and luteinizing hormone but a decrease in testosterone. The results show that the influence of indomethacin was better in the dose of 75 mg daily. The mechanism of those changes is not clear. Treatment should be at least 60 days.

Asunto(s)

RESUMEN

After publication in the literature that in vitro caffeine treatment causes damage of the normal shape of the sperm head and thereby decreases fertilizing capacity, we carried out a clinical and electron microscopic study to determine the influence of caffeine on the fertilizing capacity and sperm cell morphology. Sixty women (with infertile husbands) underwent artificial insemination by donor with frozen/thawed semen over a period of 12 months, using randomized addition of caffeine in alternate months. Fourteen women became pregnant during the 6 months they received caffeine-treated semen, whereas only 7 pregnancies occurred during the 6 months the women received semen without caffeine. Scanning electron microscopic examinations of fresh proven donor semen showed no morphologic changes caused by the in vitro caffeine treatment. However, quantitative morphologic analysis of the frozen/thawed semen was unsatisfactory because of the freezing technique and the masking effect of the protective medium. It is concluded that in vitro caffeine treatment of fertile donor semen does not damage the spermatozoa; furthermore, it seems to improve the fertilizing capacity.

Asunto(s)